1. Field of the Invention
This invention relates to a disconnect switch for use with a metal encapsulated high voltage switching installation wherein the switch includes a movable switching pin and a mating contact axially associated therewith.
2. Description of the Prior Art
In known disconnect switches of the above type, the movable switching pin is actuated by a motor drive, which requires from between 5 to 10 seconds to close the switch. The actual closing time depends on the size of the gap between the switching pin and the mating contact which, in turn, is a function of the nominal voltage.
If a disconnect switch of the present type is closed, a preliminary breakdown with a subsequent low-current arc always occurs, if the disconnect switch is operated under voltage. In such case, the burning time of the preliminary arc takes several seconds.
For disconnect switches which are suitable for voltages of up to 123 kV, the preliminary breakdown distance is so small, particularly where sulfur hexafluoride is used as the quenching and insulating medium of the metal-encapsulated installation, that the arc does not wander off while it burns. In disconnect switches for voltages higher than 123 kV and for currents of about 2000 A, the preliminary breakdown distance is larger, so that there is a definite danger that the preliminary arc will wander from the point of its origin to the grounded encapsulation of the installation.
It is, therefore, an object of the present invention to provide a disconnect switch of the above type which can be used for voltages above 245 kV and whose longer-burning arc is prevented from wandering.